The present invention relates to voussoirs having the general shape of a segment of a cylinder, which are used in particular for tunnel linings.
The tunnel linings formed by known voussoirs are of the shape of a cylinder with a radius the same as that of the voussoirs which are, themselves, segments of a cylinder. Such an arrangement has no disadvantages when it is for the construction of a very long tunnel, as the high number of voussoirs which need to be produced justifies the investments required for the manufacture of voussoirs having the predetermined shape required for the radius of the tunnel lining. This is not so in the case of a tunnel of short length or when the voussoirs are to be used to recondition or repair an existing tunnel, in particular to consolidate the roof of an old concrete lining where the side walls have to be kept, because the voussoirs then have to adapt to a pre-established, possibly variable, lining profile.
It is known, in particular from French Pat. No. 2,264,921 (corresponding to U.S. Pat. No. 4,037,417), in the name of the present assignee, to use voussoirs comprising longitudinal sides which have radial profiles with predetermined curvatures, and equipped with embossments and centering recesses. However, in these voussoirs the curvature of one side is convex and that of the other is concave and, as has already been said, they are intended exclusively for cylindrical linings whose radius is the same as that of the voussoirs.